"It was one lecture in the curriculum. Now it forms the majority of the general gastroenterology that we see in the West of Scotland."

However, because of the embarrassing nature of the condition, IBD has a low profile and doesn't attract funding for research.

It's a disease of healthier living, cleaner living, appropriate immunisations, early use of antibiotics and refrigeration of foodsDr Daniel Gaya, Glasgow Royal Infirmary

No-one knows exactly how many people suffer from it, although it's clear rates are rising and Scotland has the highest rates recorded anywhere in the world.

"We've seen a very rapid rise in children," said Dr Richard Russell. "There's been a five-fold increase in four decades - and since that study finished three years ago we've seen further cases year on year.

"Now, at the children's hospital in Glasgow, we diagnose more than one new case a week compared to five years ago when we only diagnosed one or two cases a month."

Scotland's high rates of IBD are probably due to a mixture of genetics and environment.

Some people seem to be more susceptible. An environmental trigger causes their immune system to malfunction and attack the body.

Unlike many diseases, affluence also seems to be a risk factor.

"It's a disease of healthier living, cleaner living, appropriate immunisations, early use of antibiotics and refrigeration of foods," said Dr Gaya.

"These all fail to prime you gut against the normal bacteria it would be exposed to at an early age."

There is no cure for inflammatory bowel disease, although drugs, surgery and stem cell transplants have provided long-term remission from the disease in some people.

The new register should provide a clearer picture of the number of people across the UK who have some form of bowel disease.

For more on this story, listen to The Investigation: Inflammatory Bowel Disease on BBC Radio Scotland at 13:30 on Thursday 1 August. It will also be available on BBC iPlayer.